The type of artwork he designs for the Mambo fashion label is almost cartoonish and in vivid colours, incorporating religious, political and popular culture themes.

[citation needed] Mombassa's first public showing was in a group exhibition held at Watters Gallery in Sydney in 1975 while he was still attending art college.

As Mombassa's artistic output and demand increased it prompted him to make the difficult decision to cease touring with the Mentals in April 2000.

In November 2009 HarperCollins released a biography by Murray Waldren called "The mind and times of Reg Mombassa", which includes over 200 art works.

Dog Trumpet's seventh album, Great South Road, featured the singles "Gravity", "Wallpaper", "Lonely Death Cleaning Company", "You've Heard it All Before" and "Overseas and Elsewhere".

"The Ballad of Clayton Looby" on 9 September 2022, from their album, Shadowland, which was released on 4 November 2022, on vinyl, CD and digitally worldwide by the Demon Music Group.

A video for the title track was released on 12 December 2022 Shadowland is a distinctive blending of psychedelia, folk and blues, the album probes the perils and absurdities of human existence, kicking off with the title track "Shadowland", a nervous musing on digital over-surveillance; followed by "Nina Simone", a song reflecting on romance and memory.

"F***ing Idiots" points out the shameful idiocy of our addiction to war and militarism; "The Ballad of Clayton Looby" is an anti-establishment ode to a larrikin surfer.

In 1987, with Peter, Martin Plaza and members of GANGgajang, Mombassa recorded a country music album credited to The Stetsons.

Mombassa has also appeared in a number of small Australian films, including Tender Hooks (1989), Strange Planet (1999) and Love's Brother (2004).